North Korean leader Kim Jong Un put his second naval destroyer into service and called for building a more reliable nuclear deterrent, state media reported Monday, as the United States, South Korea, and Japan began a trilateral military exercise he views as a security threat. The ship’s commissioning comes as North Korea is dialing up pressure on the US after rebuffing President Trump’s decision to scale back a drill with South Korea in a conciliatory step toward Kim, reports the AP. The destroyer Kang Kon was commissioned into North Korea’s navy in the eastern port city of Wonsan on Sunday at a ceremony attended by Kim and his teenage daughter, whom South Korea’s spy service calls his likely heir. State media photos showed the girl in a white dress and blazer walking alongside her father on a red carpet, touring the warship and posing with sailors.

The ship and the Choe Hyon, which was put into service in June, are both 5,000-ton destroyers that state media said can carry various conventional and nuclear weapons. Considered North Korea’s largest and most advanced warships, the two destroyers were likely built with Russian assistance, experts say. In July, North Korea said it test-fired nuclear-capable cruise missiles from the Kang Kon. At the ceremony, Kim said the back-to-back warship additions instilled fear in enemies as the nuclear armament of North Korea’s navy made it possible to exercise its nuclear deterrent in a more diversified, practical manner. “The enemies’ concerns will surely be deepened,” Kim said. “We must establish more clearly a powerful and reliable nuclear war deterrent, to put into practice the diverse and effective operation of our nuclear combat systems.”

After years of prioritizing ballistic missile development, Kim has increasingly turned his focus to modernizing the navy, which he admitted in Sunday’s speech lacked warships befitting its mission until a few years ago. Outside experts said the North Korean destroyers’ weapons and radar systems would enhance its offensive and defensive capabilities. Kim said North Korea is pursuing another “significant” naval advancement whose results would be unveiled in eight months. Many observers say the project could be related to Kim’s stated goal of acquiring a nuclear-powered submarine.

The US, South Korea, and Japan on Monday kicked off their five-day Freedom Edge exercise near the Korean Peninsula. South Korea’s military said the exercise is defensive in nature and meant to enhance a joint response capability against North Korean nuclear threats. At the exercise’s opening ceremony in western Tokyo, Lt. Gen. Stephen Jost, commander of the US forces in Japan, said that Washington, Tokyo, and Seoul “stand together on common interests, ready to preserve the peace and security we have built and defended for more than eight decades.”